Messages in this thread | | | Subject | Re: [PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes | From | Vlastimil Babka <> | Date | Mon, 12 Jun 2017 10:58:53 +0200 |
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On 06/08/2017 02:23 PM, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > movable_node kernel parameter allows to make hotplugable NUMA > nodes to put all the hotplugable memory into movable zone which > allows more or less reliable memory hotremove. At least this > is the case for the NUMA nodes present during the boot (see > find_zone_movable_pfns_for_nodes). > > This is not the case for the memory hotplug, though. > > echo online > /sys/devices/system/memory/memoryXYZ/status > > will default to a kernel zone (usually ZONE_NORMAL) unless the > particular memblock is already in the movable zone range which is not > the case normally when onlining the memory from the udev rule context > for a freshly hotadded NUMA node. The only option currently is to have a > special udev rule to echo online_movable to all memblocks belonging to > such a node which is rather clumsy. Not the mention this is inconsistent > as well because what ended up in the movable zone during the boot will > end up in a kernel zone after hotremove & hotadd without special care. > > It would be nice to reuse memblock_is_hotpluggable but the runtime > hotplug doesn't have that information available because the boot and > hotplug paths are not shared and it would be really non trivial to > make them use the same code path because the runtime hotplug doesn't > play with the memblock allocator at all. > > Teach move_pfn_range that MMOP_ONLINE_KEEP can use the movable zone if > movable_node is enabled and the range doesn't overlap with the existing > normal zone. This should provide a reasonable default onlining strategy. > > Strictly speaking the semantic is not identical with the boot time > initialization because find_zone_movable_pfns_for_nodes covers only the > hotplugable range as described by the BIOS/FW. From my experience this > is usually a full node though (except for Node0 which is special and > never goes away completely). If this turns out to be a problem in the > real life we can tweak the code to store hotplug flag into memblocks > but let's keep this simple now. > > Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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